The important thing is not how you regard marriage, it's how society regards marriage. It's definitely a transformation - a subtle one, but a transformation nonetheless. Fundamentally, when you're married every acquaintance you make, casual or serious, presumes that your destiny is tied to another person. I suspect your current (healthy) attitude towards marriage is at least partially shaped by your current (healthy) attitude towards destiny: you don't have firm plans and goals so the idea of coordinating your plans and goals with another human being complicates things rather than simplifying them.

Kids are the same way, in their own way. They're a collaborative project to expand and transform the partnership, fundamentally. Unfortunately society doesn't tell you this. "Do you want to have kids?" is a question completely divorced from "Are you interested in joining your life to someone else in a collaborative effort intended to better both your lives through decades of intimate, expensive, messy, inspirational and joyful struggle?" because if we phrased the question that way, everyone under about 35 these days would say "fuck to the no."